Geography - THE CARBON CYCLE

What is the Paris Agreement?

An international treaty signed by 195 countries in 2015 with the goal of keeping the increase in global temperature to well below 2 degrees C above pre-industrial levels.

What are the 3 types of carbon store?

terrestrial, oceanic and atmospheric

What is a flux in terms of the carbon cycle?

the movement of carbon between stores

What are the 3 carbon cycles?

Geological (slow)

Biogeochemical (fast)

Oceanic

Outline the geological carbon cycle

C held in the mantle released into atmosphere as CO2 when volcanoes erupt.

Carbonic acid produced; dissolves rocks releasing bicarbonates.

Rivers transport weathered calcium and carbon sediment to oceans.

C in organic matter sinks to sea floor and dies, building strata of coal, chalk and limestone.

What are the 4 key processes in the biogeochemical carbon cycle?

photosynthesis

respiration

decomposition

combustion

What are the 3 oceanic carbon pumps?

Biological pump

Physical Pump

Carbonate pump

What is inorganic carbon?

found in rocks as bicarbonate and carbonate (earths largest carbon store)

What is organic carbon?

found in plant material

What is the gaseous form of carbon?

found as CO2, CH4 and CO

What are the 3 forms of carbon?

inorganic

organic

gaseous

Why are CO2 fluxes greater in the northern hemisphere?

contains greater landmass and temp variations than S hemisphere

How does the biological carbon pump work?

move carbon dioxide from the ocean surface to marine plants called phytoplankton through photosynthesis.

phytoplankton consumed

diel vertical migration

marine snow

How does the carbonate pump work?

marine organisms like plankton and corals extract calcium and bicarbonate ions from seawater to build shells.

shells and skeletons fall to sea floor when they die forming sediments

What is thermohaline circulation?

global network of deep ocean currents driven by differences in seawater density which is determined by temperature (thermo) and salinity (haline)

Outline how thermohaline circulation works

Main current begins in cold polar oceans where surrounding seawater sinks due to higher density.

Current divides - N into indian ocean, W into the western pacific

2 branches warm and rise as they travel N and then loop back to the S and W.

Current recharged as it passes Antarctica by cold salty dense water.

Warmed surface waters continue circulating around globe. On return to N atlantic they cool and cycle begins again.

What are the threats to thermohaline circulation?

warming sea surface temp - water doesn’t cool and sink - currents not recharged

less salty water - less dense - doesn’t sink

Impacts of reduced thermohaline circulation

changes in ocean acidity

reduced nutrient movement

increased atmospheric CO2 (+ve feedback loop)

changes in weather patterns

Why did the Gulf Stream slow down?

melting arctic ice increases amount of freshwater entering N atlantic

therefore salinity decreased, preventing cold water sinking there

this meant there was nowhere for the warm gulf stream waters to go - the N atlantic was losing its pulling effect

Give examples of terrestrial carbon sequestration

terrestrial organisms

wetlands

mangroves

boreal forest

rocks

permafrost

rainforests

How does terrestrial carbon sequestration work?

photosynthesis → carbon fixation → death → soil storage

Give examples of marine carbon sequestration

carcasses

marine snow 

shells (calcium carbonate)

How does marine carbon sequestration work?

surface diffusion → assimilation (to make shells) → death → sedimentation

photosynthesis → consumption → death → marine snow →storage as sediment or rock

Give example of artificial carbon sequestration methods

carbon capture technology

bioenergy

How does bioenergy work as a method of carbon sequestration?

plant trees → grow → burn → repeat

How does carbon capture technology work as a method of carbon sequestration?

direct air capture

capture → concentration → storage or reuse in product

What does carbon fixation do ?

Turns gaseous carbon (CO2) into living organic compounds that grow.

Why are mangroves good carbon sequesterers?

their soils are anaerobic due to being submerged twice a day by high tides

Why is permafrost a good carbon store?

microbe activity only active is surface layer of soil when it thaws

Rainforest dying off positive feedback cycle

temp rise → more drought and wildfires →more trees die, releasing CO2 →fewer trees means lesswater in atmosphere → rainfall decreases

Forest dieback positive feedback loop

drying of forest vegetation → forest dieback → less evapotranspiration →less rainfall

Phytoplankton death positive feedback loop

phytoplankton death → less food for zooplankton and secondary consumers →krill keystone species death → less diel vertical migration → less marine snow →less carbon held in deep oceans → ocean acidification and temp change

Warming of ocean water negative feedback loop

warming ocean water → less water cools and sinks → ocean currents not recharged →less CO2 absorbed by oceans →slower ocean acidification →benefit to coral reefs

Give examples of greenhouse gases

CO2 , CH4, NO, H2O (water vapour)

How does the natural greenhouse effect work?

short wave radiation passes through atmosphere

some short wave radiation absorbed

some converted into long wave radiation

some long wave radiation passes back into space

some long wave radiation reflected off greenhouse gases back to Earth, heating it

What is radiative forcing effect and which GHG has the highest?

ability to hold onto heat - CO2

What are the warming powers of the other GHG’s compared to CO2?

Halocarbons x3000 more powerful

N2O x250

CH4 × 21

Sources of CO2

burning FF’s

deforestation

Sources of CH4

gas pipeline leaks, rice farming, cattle farming

Sources of N2O

jet engines, vehicles, fertilisers, sewage plants

Sources of halocarbons

industry, solvents and cooling equipment

Give examples of F gases 

Hydrofluorocarbons (HFC’s)

Perfluorocarbons (PFC’s)

Sulfur Hexafluoride

Why are F gases bad?

High atmospheric lifetime 

High global warming potential (GWP)

What are RCP’s?

Representative Concentration Pathways

include range of assumptions inc pop growth, economic development, technological innovation and attitudes to social and env sustainability

Represent best case to worst case scenarios

Features of healthy soil

dark crumbly and porous

contain many worms and other organisms

contain more C or organic matter

sequester C

retain moisture, which regulates soil temp during heatwaves + reduces effects of droughts

What is primary productivity?

the rate at which plants produce biomass

Consequences on European climates due to climate change

avg temp increase - largest increase in E and N Europe in winter and S Europe in summer

ppt - increase in N Europe , decrease in S Europe

extreme weather likely to increase in intensity and frequency

What is arctic amplification?

the arctic is warming twice as fast as the global average

Melting permafrost positive feedback cycle

melting permafrost → CO2 and CH4 released → increased greenhouse effect → increased warming of tundra surface and ocean waters

Give examples of primary energy sources

consumed in their raw form

coal

oil

natural gas

nuclear

Give examples of secondary energy sources

electricity

refined oil eg petrol

Define energy security

being able to access reliable and affordable sources of energy

Why is the UK energy insecure?

declining domestic north sea oil and gas means we are more dependent on imported energy

Give examples of non renewables

coal

oil

gas

Give examples of renewables

solar

wind

wave

Give examples of recyclable energy sources

reprocessed uranium and plutonium

biomass

2 problems with the UKs current energy mix 

majority comes from non renewables

high reliance on imported fuels make UK politically vulnerable

What factors can affect energy consumption?

physical availability

cost

technology

political considerations

level of economic development

environmental priorities

What is an energy pathway?

describes flow of energy between a producer and consumer and how it reaches the consumer eg pipeline

Name 4 different energy players

energy TNCs

OPEC

National governments

Consumers

Role of energy TNCs

exploit and distribute energy resources

own supply lines and invest in distribution and processing of raw materials

respond to market conditions to secure profits for their shareholders

Examples of old and new energy TNC players

old- BP, Shell (UK), Exxon Mobil (US)

new - Gazprom (russia), Petrobras (Brazil), Reliance (India)

What is OPEC’s role

Organisation of petroleum exporting countires

co ordinate and unify the petroleum policies of its members

secure efficient, economic and regular supply of petroleum to customers

steady income for producers

fair return for investors

Example of what OPEC does

set oil production quotas to respond to economic conditions - boosting supplies when demand rose and reducing them when demand fell 

eg kept prices low 2012-16 to compete with USA fracking oil production

Role of national governments as an energy player

meet international obligations while securing energy supplies for nations present and future

support country’s economic growth

regulate role of private companies

set environmental priorities

Examples of national govts being an energy player

EU govts aim to fulfil CO2 emissions targets and reduce fossil fuel dependency 

EDF (france) and China General Nuclear are 2 govt backed energy TNCs involved in Hinkley Point C.

Role of consumers as an energy player

create demand - purchasing choices often based on cost

have some power over oil companies - eg by buying electric cars 

protests against fracking and nuclear

What is a transit state?

a country or state through which energy flows on its way from producer to consumer

What is the ESPO?

East Siberia Pacific Ocean pipeline

exports crude oil from Russia to China, S Korea and Japan

example of an energy pathway

What is Nord Stream?

Pipeline running from Russia to Europe along the Baltic sea bed

1/3 of EU gas imported from russia

highly exposed to sabotage

What is a chokepoint?

a narrow sea channel or convergence where key transport routes can easily be disrupted

Give some examples of energy choke points

Panama Canal

Bab el Mandab strait

Suez Canal

Strait of Malacca

Why is the Panama Canal an energy choke point

connects atlantic and pacific

key for US energy exports to Asia

congestion

climate sensitive - reliant on freshwater lakes 

tankers may need to redirect around Cape Horn/Suez - shipping costs spike

Why is the Suez canal an energy choke point?

links red sea and med

crude oil and refined products from middle E and Asia shipped to Europe and N america

narrow , congested , can cause immediate global disruption 

eg Ever Given incident 2021

tankers reroute around cape of good hope - immediate spikes in shipping rates and oil/gas prices

Why is the Bab el Mandeb Strait an energy chokepoint?

20 mile strait conneting Red sea to Arabian Sea

carries 6-7 million barrels per day of crude and refined products

piracy threats

ongoing conflict in Yemen

blocks Middle East exports to europe/USA via suez

What is a proxy war?

a war instigated by a major power that is not always directly involved in the fighting. Proxy wars common due to international tension over oil and gas eg Syrian conflict

Give 4 examples of unconventional fossil fuels

deep water oil

tar sands

shale gas

oil shale

What is oil shale?

deposits of organic compounds called kerogen in sedimentary rocks that have not undergone sufficient pressure, heat or time to become conventional oil

Where are the largest reserves of tar sands

Canada - with 3 major deposits in alberta

Who are the players in Canadas tar sands

governments

oil companies

environmental pressure groups

local communities

How is the Canadian governent a player in tar sands

promote tar sands for energy security and economic development

Costs and benefits for local communities to tar sands

new jobs

fears over pollution in Athabasca river, atmospheric toxins and increased incidence of rare cancers and auto immune diseases

disruption to traditional ways of life

housing crisis as thousands of workers have been shipped in

Costs of exploiting tar sands

very energy intensive

only viable when the price of crude oil exceeds US$40 a barrel

uses a lot of water

1.8m tonnes toxic wastewater produced every day

destroys ecosystems inc taiga forest

Benefits of exploiting tar sands

alternative source of oil

offers energy security for canada and usa

can serve as fuel stopgap until more renewable energy sources become viable

earns revenue for local and national economies

Implications for carbon cycle from tar sand extractions

carbon emissions rise due to extraction, production and use

carbon absorption falls due to deforestation

Environmental impacts of tar sands mining

destroys forest and peat bogs

 toxic tailing/waste material ponds created

caribou populations have declined sharply in areas of oil extraction

How is the UK reducing FF use?

increase renewable energy

developing new nuclear eg Hinkley Point C

reducing energy use eg using LEDs

recycling energy which would normally be wasted

Costs and benefits of nuclear

nuclear disasters eg Fukushima

radioactive waste products

provides many jobs eg 25000 Hinkley Point C

low operational costs

take up small land area (compared to wind/solar)

operational longer than wind turbines eg Hinkley Point C 60 yrs

costs and benefits of wind power 

not always windy

take up a lot of area

renewable

can power 1million homes - Hornsea Project 1

Costs and benefits of solar power

take up a lot of land area

more suited to some countries than others

expensive

eg chapel lane solar farm powers 60000 homes in bournemouth

Strengths of biofuels

renewable

lower emissions than FFs

biodegradeable

easily grown , doesn’t need specialist machinery

Weaknesses of biofuels

takes land from food production

needs pesticides and fertilisers which use FFs in production - not carbon neutral

requires lots of water

forest cleared to grow crop - loss of carbon sink

Opportunities created by biofuels

positive multiplier effect in rural regions

infrastructure improvements often provided by growers

Threats to biofuels

food shortages occur which lead to higher food prices

What is carbon capture and storage (ccs)

gas transported to a site where its compressed , stored and piped to an injection well where its injected into geological reservoirs in liquid form

What are hydrogen fuel cells

fuel cells convert chemical energy in hydrogen to electricity with pure water as a by product 

Impacts of deforestation on the water cycle

decreased infiltration

increased runoff and erosion

flood peaks higher and lag time shorter

increased discharge leads to flooding

annual rainfall decreased and seasonality of rainfall increases

Impacts of deforestation on soil health

raindrop impact washes finer particles of clay and humus away

coarser and heavier sands left behind

CO2 released from decaying woody material

biomass lost due to reduced plant growth

rapid soil erosion leads to nutrient loss

Impact of deforestation on atmosphere

turbulence increased as heated ground induces convectional air currents

o2 content reduced and lower transpiration rates

reduced evapotranspiration makes it less humid